I have a 90 LS. I noticed it was running rough on Monday, so I checked the ECU codes. I was getting a ‘1’ so I replaced the O2 sensor last night. That did not make any improvement and on the way to replace the O2 sensor, it was running rougher and rougher. After replaciing the O2 sensor and replacing the plugs, it became evident that #2 cylinder was not firing. The plug is just wet with fuel but no evidence of combustion.
So now it is running on only 3 cylinders. I have replaced the cap/rotor/coil/igniter all in the last month or two and it was running fine. I tend to not think that this is the problem, the others are firing fine. I was also able verify that #2 is getting spark.
It seems like either way too much fuel is getting dumped in there, or maybe just raw fuel, no air.
Anyone have any ideas?